Waste-heat boiler

ABSTRACT

An improved waste-heat boiler for cooling and recovering heat from hot gases. The improvement comprises employing two concentric tubes for delivering coolant liquid, the coolant liquid from the inner concentric tube under pressure serving as feed to a plurality of ejectors which draw coolant liquid from the outer concentric tube and by means of an arrangement of spray nozzle arms, direct the coolant against the bottom plate of the boiler and the inlet ends of the heat exchange tubes connected thereto.

United States Patent Ter Haar 51 May 16, 1972 [54] WASTE-HEAT BOILERLeonard W. Ter l-laar, Hague, Netherlands t [73] Assignee: Shell OilCompany, Houston, Tex.

[22] Filed: Dec. 30, 1970 [2]] App], No.: 102,588

[72] Inventor:

[30] Foreign Application Priority Data Jan. 21, 1970 Netherlands..70008l2 [52] US. Cl. ..l22/7 R, 122/40 [51] Int. Cl ..F22b 1/18 [58]Field ofSearch ..l22/7 R, 40,4], 114

[56] References Cited UNITED STATES PATENTS 2,790,428 4/ 1957 Buttler122/40 X 2,967,515 1/1961 Hofstede et al i 22/7 Primary Examiner-KennethW. Sprague AttorneyGlen R. Grunewald and John H. Colvin [57] ABSTRACT Animproved waste-heat boiler for cooling and recovering heat from hotgases. The improvement comprises employing two concentric tubes fordelivering coolant liquid, the coolant liquid from the innerconcentrictube under pressure serving as feed to a plurality of ejectors whichdraw coolant liquid from the outer concentric tube and by means of anarrangement of spray nozzle arms, direct the coolant against the bottomplate of the boiler and the inlet ends of the heat exchange tubesconnected thereto.

5 Claims, 4 Drawing Figures PMENTEDmvsnsvz 3.662.717

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INVENTORI LEONARD w. TER VHAAR HIS ATTORNEY P'A'TENFEnm 16 m2 3.662.717

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INVENTOR:

LEONARD W. TER HAAR FIG. 4 2;

, HIS ATTORNEY WASTE-HEAT BOILER BACKGROUND OF THE INVENTION 1 Field ofthe Invention This invention relates to an improved apparatus forcooling and abstracting heat from high temperature gases with thegeneration of steam at superatmospheric pressures, e.g., pressures offrom 5-l50 atmospheres. The waste-heat boiler herein provided isparticularly suitable for the recovery of sen sible heat from hot,soot-containing gases obtained by partial combustion of hydrocarbonswith oxygen or oxygen-enriched air, e.g., hydrogen and carbonmonoxide-containing synthesis gas obtained from an oil gasificationprocess.

2. Description of the Prior Art Crude synthesis gas produced by thepartial combustion of hydrocarbons generally is discharged from thereactor at a temperature of from l,300 to 1,400 C. or higher, thusmaking it an obvious source of potential'energy. The thermal energy insynthesis gas, however, can be recovered only with great difficultyutilizing conventional heat exchangers, because of the presence in suchgas of large amounts of soot (i.e., free carbon), often up to 5 percentor more, which tends to deposit on the inside of the exchange tubes. Anumber of waste-heat boilers have been proposed forum in recovering heatfrom such gases, for example, the apparatus described in US. Pat. No.2,967,515 to Hofstede et al. in which helically coiled tubes areemployed, or that described in copending US. application Ser. No.87,451, filed Nov. 6, 1970, in which a combination of straight andhelically coiled heat exchange tubes are used. In boilers of thisgeneral design, hot gas obtained from the partial combustion ofhydrocarbons is introduced into the waste-heat boiler and flowed throughone or more straight and/or helically coiled tubes connected at theirinlet ends to the bottom plate of the boiler. Coolant liquid is normallyadmitted into the waste-heat boiler through a vertical, radially spacedtube which can be provided with a nozzle so that the coolant isdischarged against the hot bottom plate, after which it ascends upwardinto the space formed between the coolant tube and the shell of thewaste-heat boiler, thereby cooling the straight and/or helically coiledtube or tubes accommodated therein. j

In view of the high temperatures to which the bottom plate and gas inletends of theheat exchange tubes are exposed, it is of obvious importancethat these surfaces be adequately cooled. However, this has often provedto be difficult in prac tice, particularly in waste-heat boilers whereina plurality of heat exchange tubes are connected to the bottom plate,because of the interference of the tubes with the coolant flow whichresults in uneven cooling. Conventional Waste-heat boilers equipped witha single coolant supply tube suffer from a further deficiency in that inthe event of an interruption in the flow of coolant, e.g., because of anoperational breakdown, high pressures and temperatures rapidly developin the boiler creating a potentially hazardous situation. The presentinvention provides a means of overcoming these problems.

SUMMARY OF THE INVENTION It has now been found that the heat exchangetubes and bottom plate of a waste-heat boiler can be efficiently cooledby the use of two concentric cooling tubes connected to a novelejector-nozzle arrangement as hereinafter described. A plurality ofejectors are employed in this arrangement, issuing from the inner of theabove-mentioned concentric tubes. These ejectors are fed by coolantunder pressure from the inner concentric tube and serve to draw coolantfrom the outer concentric tube. The coolant discharged from the ejectorsand that drawn from the outer tube is directed by means of aplurality ofspray nozzle arms against the bottom plate of the waste-heat boiler andthe inlet ends of the heat exchange tubes, thereby cooling the same.

DESCRIPTION OF PREFERRED EMBODIMENTS In a preferred embodiment of theinvention, the heat exchange tubes comprise two or more helically coiledtubes each connected to a straight tube through which the hot gas isinitially flowed. The straight tubes may be of relatively short lengthand thus serve merely as connecting pieces, or may be selected longer,if desired, for constructional reasons or to reduce the temperature ofthe gases before they enter the first coil of the helically coiledtubes.

In one embodiment of the waste-heat boiler of the invention, a centralejector issuing vertically from the lower end of the inner concentrictube is employed, together with at least one ancillary ejector issuinglaterally from the lower end of said tube. In this embodiment, the spraynozzle anns extending from the outer concentric tube will be positionedso as to cooperate with and receive coolant from the ejectors, and todirect coolant streams against the bottom plate and the inlet ends ofthe exchange tubes. The use of a central and plurality of ancillaryejectors and corresponding central and ancillary spray nozzle armsensures even cooling of the bottom plate and inlet ends of the exchangetubes. This is particularly the case if the number of ancillary ejectorsis equal to the number of straight tubes and these ejectors cooperatewith the spray nozzle arms arranged symmetrically and issuing betweenthe straight tubes. These arms are preferably curved in such a way thatthe outflowing coolant acquiresa direction of movement with a horizontalvelocity component. I

In the aforedescribed embodiment, the coolant in the outer concentrictube can be used to provide a measure of cooling even if the flow ofcoolant in the inner tube is interrupted. This can be convenientlyaccomplished, for example, by connecting the outer tube to a storagevessel containing coolant located above the waste-heat boiler, so that acontinued supply of coolant is ensured even if coolant pressure in theinner tube should fail.

In a specific embodiment of the apparatus, the space of the waste-heatboiler in which the'ejector nozzle arrangement is accommodated, has, atthe point of connection of the ejectors and nozzles to the concentrictubes, a free cross-sectional area which does not exceed 30 percent ofthe space accommodating the helical coils. This results in an improvedflow of the coolant through the waste-heat boiler. p

The above free cross-sectional area may be given the desired value byarranging baffle plates, which, for example, with'a waste-heat boilerhaving four straight tubes, may have the shape of a curved shield andbedisposed symmetrically along the wall of the space, the concave sidefacing the wall.

If desired, the temperature of the gases to be cooled may be lowered byinjecting a coolant, for example, water, into the gases after they haveleft the reaction chamber. This precooling of the gases may be carriedout continuously or temporarily, for example, if difficulties should beencountered in supplying coolant to the waste-heat boiler.

The invention will now be further explained with reference to thediagrammatic drawings, which illustrate different embodiments of theapparatus according to the invention.

FIG. 1 is a diagrammatic representation of an apparatus for the partialcombustion of hydrocarbons and the cooling thereof.

FIG. 2 is a side view of an embodiment of the waste-heat boiler.

FIG. 3 shows a cross section of an embodiment-of the wasteheat boilerthrough the space accommodating the straight tubes, i.e., immediatelyabove the outflow point of the spray nozzle arms with which theancillary ejectors cooperate. The waste-heat boiler depicted has fourhelical coils each connected to a straight tube.

FIG. 4 shows a cross section of an embodiment of the wasteheat boilerthrough the space accommodating the straight tubes, i.e., at somedistance above the level at which the ejector-nozzles are connected. Thewaste-heat boiler is provided with four helical coils each connected toa straight tube and with four baffle plates which are arranged in thespace accommodating the straight tubes and which extend near to thebottom plate.

Referring now to FIG. 1, part A represents a reactor for partiallycombusting hydrocarbons which is provided with fuel supply line qleading to burner part A of the reactor, and oxygen supply line b.Steam, if used, can be supplied through either q and/or b. Part B is aconnection between the reactor and connecting piece C. The hot gases arepassed through the connection B and the connecting piece to waste-heatboiler D which is provided with two straight tubes and two helicalcoils, discharges c and d for the cooled gases, inlets e and f for thecoolant (e.g., water) and outlet k for the coolant. The straight tubesare designated by g and h, and the helical coils by i and j.

FIG. 2 is a side view of a part of the embodiment of the waste-heatboiler. The waste-heat boiler comprises cylindrical vessel 1 havingbottom plate 2, placed on connecting piece 3 which is provided with gassupply line 4. The waste-heat boiler further comprises concentric tubes5 and 6 through which the coolant is supplied (under pressure in tube6), the bottom ends of which are linked to a spray nozzle comprisingcentral ejector 11 which cooperates with central arm 12 and twoancillary ejectors 7 and 8 which cooperate with arms 9 and 10,respectively. The coolant, preferably water, is supplied throughconcentric tubes 5 and 6 and is sprayed against the bottom plate by thearms 9, l0 and 12, after which it flows upwards thereby cooling thestraight tubes designated by 13 and 14.

FIG. 3 is a cross section through the space accommodating the straighttubes, taken immediately above the discharge point of the spray nozzlearms of the embodiment shown in FIG. 2, but which has four helicalcoils, each connected to a straight tube. The cross section shows thefour straight tubes, the central arm of the spray noule and the fourarms with which the ancillary ejectors cooperate. In the drawing,reference numerals 21, 22, 23 and 24 designate the straight tubes, 25 isthe central arm of the spray nozzle and 26, 27, 28 and 29 are the armswith which the ancillary ejectors cooperate. The outflowing coolantacquires a horizontal component of movement as a result of the lateralcurvature of arms 26, 27, 28 and 29.

FIG. 4 is a cross section through the space accommodating the straighttubes of an embodiment of the waste-heat boiler having the configurationshown in FIG. 3, but in which the cross section is taken at somedistance above the point at which the ejector-nozzle arrangement isconnected. The cross section shows the four straight tubes, theconcentric tubes through which the coolant flows and the baffle platesfor the coolant. In the drawing the reference numerals 31, 32, 33 and 34designate the straight tubes, 35 is the inner tube through which thecoolant flows under pressure, 36 is the outer tube from which thecoolant is drawn by the ejectors, and 37, 38, 39 and 40 are the baffleplates for the coolant.

I claim as my invention:

1. A waste-heat boiler for generating vapors from a coolant by heattransfer from a high temperature gas which comprises: (1) a closedvessel having a bottom plate and an outlet means for dischargingvaporized and liquid coolant; (2) a plurality of straight tubes intowhich hot gas is introduced, each connected at its inlet end to thebottom plate and at its outlet end to a helically coiled tube throughwhich the gas is flowed and discharged from an upper part of saidvessel; (3) two vertical concentric tubes for supplying coolant liquidmounted within said vessel in a radially spaced relation thereto anddefining with said vessel an elongated annular space in which saidstraight and helically coiled tubes are situated; (4) a central ejectorand plurality of ancillary ejectors by means of which coolant is drawnfrom the outer of said concentric tubes, said ejectors issuing from thelower end of the inner of said concentric tubes and being fed by coolantsupplied therefrom; (5) a central spray nozzle arm and plurality ofancillary spray nozzle arms extending from the lower end of the outerconcentric tube, positioned so as to receive the coolant discharged fromthe e ector and drawn from the outer concentric tube, and

discharge the same against the bottom plate and the inlet ends of saidstraight tubes.

2. The waste-heat boiler of claim 1 wherein the number of ancillaryejectors is equal to the number of straight tubes and the ancillaryspray nozzle arms are arranged symmetrically and issue between thestraight tubes.

3. The waste-heat boiler of claim 2 wherein the spray nozzle arms arecurved laterally so that the discharged coolant acquires a direction ofmovement with a horizontal velocity component.

4. The waste-heat boiler of claim 1 wherein the space at the point theejectors and spray nozzle arms are connected to the concentric tubes hasa free cross-sectional area of less than 30 percent of the spaceaccommodating the helical coils.

5. The waste-heat boiler of claim 1 wherein baffle plates are present inthe space accommodating the straight tubes.

1. A waste-heat boiler for generating vapors from a coolant by heattransfer from a high temperature gas which comprises: (1) a closedvessel having a bottom plate and an outlet means for dischargingvaporized and liquid coolant; (2) a plurality of straight tubes intowhich hot gas is introduced, each connected at its inlet end to thebottom plate and at its outlet end to a helically coiled tube throughwhich the gas is flowed and discharged from an upper part of saidvessel; (3) two vertical concentric tubes for supplying coolant liquidmounted within said vessel in a radially spaced relation thereto anddefining with said vessel an elongated annular space in which saidstraight and helically coiled tubes are situated; (4) a central ejectorand plurality of ancillary ejectors by means of which coolant is drawnfrom the outer of said concentric tubes, said ejectors issuing from thelower end of the inner of said concentric tubes and being fed by coolantsupplied therefrom; (5) a central spray nozzle arm and plurality ofancillary spray nozzle arms extending from the lower end of the outerconcentric tube, positioned so as to receive the coolant discharged fromthe ejector and drawn from the outer concentric tube, and discharge thesame against the bottom plate and the inlet ends of said straight tubes.2. The waste-heat boiler of claim 1 wherein the number of ancillaryejectors is equal to the number of straight tubes and the ancillaryspray nozzle arms are arranged symmetrically and issue between thestraight tubes.
 3. The waste-heat boiler of claim 2 wherein the spraynozzle arms are curved laterally so that the discharged coolant acquiresa direction of movement with a horizontal velocity component.
 4. Thewaste-heat boiler of claim 1 wherein the space at the point the ejectorsand spray nozzle arms are connected to the concentric tubes has a freecross-sectional area of less than 30 percent of the space accommodatingthe helical coils.
 5. The waste-heat boiler of claim 1 wherein baffleplates are present in the space accommodating the straight tubes.